The invention relates to a high pressure gas cooler for a refrigerant circuit of a motor-vehicle air-conditioning system, and more particularly but not exclusively to a gas cooler for supercritical CO2 refrigerant circuit.
The underlying technology and problems of such a gas cooler are described in detail in the offprint by Jxc3xcrgen Wertenbach, Jxc3xcrgen Mauxc3xa9 and Wolfgang Volz xe2x80x9cCO2 Refrigeration Systems in Automobile Air-Conditioningxe2x80x9d. In this case, according to FIG. 2 of this offprint, reference is made to the so-called RACE project. The invention deals with a further development of the result of this RACE project; the features to which the invention relates in the preamble of claims 1 to 3 are presented in FIG. 4 of this offprint.
In brief, problems are encountered in the configuration of a motor-vehicle climate-control system when the intention is to replace the old refrigerants, for example R134a which is generally used in the case of motor-vehicle air-conditioning systems, by carbon dioxide, amongst other things in order to reduce the greenhouse effect. In the scope of the aforementioned RACE project, it has been found that, when CO2 is used as the refrigerant, the best efficiency can be obtained with the circuit according to FIG. 4 of the cited offprint. In comparison with known motor-vehicle air-conditioning systems which use conventional refrigerants, an inner heat exchanger exchanging heat between the high-pressure and low-pressure sides is added as a new component. While, further, in the case of conventional refrigerant circuits, manifolds can equally well be used on the low-pressure side and on the high-pressure side, a manifold on the low-pressure side is preferred for reasons of optimum efficiency in the operating mode to which the invention relates. For details, reference is again expressly made to the offprint indicated above.
The object of the invention is to make it possible to accommodate the following aspects at least individually, but as far as possible in combination or in totality:
1. There should be the fewest possible pressure-proof lines needed for high-pressure operation. Reducing the number of pressure-proof connecting lines also leads in this regard to fewer screw connections of these connecting lines; such screw connections are needed not only because of the high-pressure operation, but also because CO2 diffuses into conventional tube connections, in which elastomer seals are employed, and this can lead to explosive eruptions of the elastomer sealing means.
2. The new element, an inner heat exchanger, should as far as possible not increase the installation space required in the motor vehicle at all, or at most slightly.
3. The general use of a manifold on the low-pressure side should in this regard be accommodated so as to save space and cost.
4. The arrangement should be organized so that, in an existing motor vehicle which is still equipped with a conventional motor-vehicle air-conditioning system, the installation space can also be utilized for an air-conditioning system having the elements needed for operation with CO2, by replacing the corresponding components.
According to one aspect of the invention there is provided a high pressure gas cooler for a motor-vehicle air-conditioning system having a refrigerant circuit comprising, in the flow direction of the refrigerant, the gas cooler, an inner heat exchanger operable. to exchange heat between the high-pressure and low-pressure sides, wherein the gas cooler and the inner heat exchanger are combined to form a single unit.
According to another aspect of the invention there is provided a high pressure gas cooler for a high-pressure refrigerant circuit of a motor-vehicle air-conditioning system, the refrigerant circuit having, in the flow direction of the refrigerant, an inner heat exchanger exchanging heat between the high-pressure and low-pressure sides, which communicates via the low-pressure side of the inner heat exchanger with the intake side of the compressor, wherein the gas cooler, the inner heat exchanger and the manifold on the low-pressure side are combined to form a single unit.
According to a third aspect of the invention there is provided a high pressure gas cooler for a refrigerant circuit of a motor-vehicle air-conditioning system, the refrigerant circuit having, in the flow direction of the refrigerant, the gas cooler, an inner heat exchanger exchanging heat between the high-pressure and low-pressure sides, and a manifold on the low-pressure side, which communicates via the low-pressure side of the inner heat exchanger with the intake side of the compressor, wherein the gas cooler and the manifold on the low-pressure side are combined to form a single unit.
Certain dependent claims, for example claims 2 to 4, concern a basic structure of the gas cooler according to the invention which is preferred both in terms of production, compactness and using the same component parts, with further dependent claims, for example claim 5, covering further standardization of the components.
The xe2x80x9cfirstxe2x80x9d heat-exchange tubes of the gas cooler are in principle ribbed; claims such as claim 6 however cover embodiments where the inner heat exchanger can be configured entirely without ribbing while obtaining an especially compact unit.
As previously, in the case of conventional motor-vehicle air-conditioning systems, heat exchangers employing flat tubes are preferably used, see for example claim 7.
Depending on whether these flat tubes communicate with the low-pressure side or the high-pressure side, they are expediently arranged with differing lengths of their ends, so as hence to have the option of connecting to different chambers for the low-pressure side and the high-pressure side.
Alternative embodiments allow the flat tubes having shorter lengths of their free ends to have refrigerant applied to them.
Claims 12 to 14 concern preferred design embodiments of the manifold of the inner heat exchanger.
While the embodiments claimed so far deal with the basic concept of claim 1, which is also contained in claim 15, claims 40 to 44 concern further developments of claim 39, which is likewise included in claim 15.
According to claim 40, use is firstly made of arranging the manifold on the low-pressure side along the bank of xe2x80x9cfirstxe2x80x9d heat-exchange tubes of the gas cooler, that is to say transversely with respect to these heat-exchange tubes, while the inner heat exchanger should in fact preferably be arranged at the end side on the bank of the gas cooler, that is to say essentially with the same alignment of its xe2x80x9csecondxe2x80x9d heat-exchange tubes.
As claimed in claim 41, an intermediate channel is in this case provided between the gas cooler and the manifold and, according to whether the inner heat exchanger is arranged above or below the gas cooler, this channel carries out the necessary flow-related interconnection of the refrigerant with minimal design outlay and hence saves on external lines for the CO2 refrigerant by integrated line routing. Claims 42 and 43 concern preferred further developments in relation to this. In this regard, claim 43 is distinguished in that accumulation of compressor lubricant which has entered is avoided by the simplest of means, while optionally even avoiding a known immersed line (cf offprint from Volkswagen AG xe2x80x9cRACE Projectxe2x80x94Final Technical Task Report of Tasks 7, 15 and 16xe2x80x9d by Dr H. Rxc3x6he, B. Adiprasito and Dr U. Brennenstuhl of Jul. 17.07.1997, in particular FIG. 1).
Claim 44 gives a general formulation of two basic principles which have already identified above, and which according to the invention should be satisfied as far as possible.